The interface composition system for a solid propellant rocket motor grain and insulation is generally comprised of an embedment powder and an embedment resin which comprise an embedment system. A compatibility between the grain composition and the embedment system is necessary since this system functions as an interface between the propellant grain and the insulation system. Requirements of an embedment system include a high peel strength and a resistance to penetration by or absorption of catalyst components or casting solvent components contained in the propellant composition. Without proper peel strength and resistance to penetration the bond strength to the propellant and insulation is adversely effected. The burning rate of the propellant grain would also be adversely affected as well as the smooth burning rate because of poor adhesion to the embedment system.
An embedment system for use in conjunction with a crosslinked, carboranyl-catalyzed, composite-modified, double-base propellant composition differs from the propellant composition with which it is used in the following aspects: the embedment powder contains no carboranyl burning rate accelerator, no aluminium whiskers, and the particle size of the ammonium perchlorate has a considerably larger weight-mean-diameter. The other portion of the embedment system is an embedment resin portion composed of bisphenol A-epichlorohydrin (EPON 828) and epoxidized Dimer* acid (EPON 871). (Emery Industries of Cincinnati, Ohio is a major supplier of dimerized oleic acid which is marketed as Dimer* acid.) The curative presently used consists of a blend of meta-phenylenediamine, methylenedianiline, isopropyl meta-phenylenediamine and dinitrophenol as accelerator. This sytem is a diamine-cured epoxy embedment system.
The above described embedment system has several limitations and has proven to be unsatisfactory because of lower than required peel strength and a lower resistance to penetration by an absorption of catalyst and the casting solvents from the propellant composition.
Therefore, an object of this invention is to provide an embedment system for composite-modified double-base propellant composition which has superior characteristics to the diamine-cured epoxy embedment resin.
A further object of this invention is to provide a polyimide embedment system for composite-modified double-base propellant which has superior characteristics when compared to the characteristics of a diamine-cured epoxy embedment system.